SAN JOSE -- Only days before the start of the NFL season, the Santa Clara County District Attorney's Office is leaning toward prosecuting San Francisco 49ers star linebacker Aldon Smith on charges of possessing illegal assault rifles -- charges that carry a range of possible punishments, from probation to three years in jail.ï»¿

Smith bought the weapons in Arizona where they are legal, but allegedly failed to modify them to comply with California's stricter gun laws, sources familiar with the case said. The three guns were discovered by Santa Clara County sheriff's deputies after a house party hosted by Smith and his roommate last summer, during which the linebacker was stabbed and two partygoers were shot by gang members who crashed the party.

Sources familiar with the Smith matter say the Rosen administration, leery of appearing too soft on the wealthy, is close to making a final decision about charging Smith after fielding accusations of pandering to the rich by not charging Brooks.

"We're not treating anyone differently," said Assistant District Attorney Scott Tsui, making it clear that the DA did not play favorites no matter who is charged. In the Brooks case, no charges were filed, partly because the linebacker claimed he acted in self-defense when he smashed teammate Lamar Divens three times in the head with a beer bottle, leaving him bloodied and requiring stitches.

The DA prosecuted Berg. A judge last week dismissed sexual assault charges against him after ruling that his wife (and accuser) was lying.

The risk in the Smith case, the sources said, is that in an effort to avoid the appearance of giving the linebacker special treatment, prosecutors may wind up treating him more harshly than they would someone who isn't a celebrity.

That's because Smith isn't just a suspect -- he's also a victim and a key witness in the stabbing and shooting cases against the gang members. Prosecutors often decline to charge such witnesses with relatively minor crimes. The linebacker told deputies he is a gun collector and said he fired one of the rifles in the air in self-defense to try to break up the party after being shot at and stabbed.

"I just really focus on what I focus on, and that's football," Smith said Wednesday from the team's training facility in Santa Clara. "I'm focusing on playing against Green Bay" in Sunday's season opener.

The late-night party, which drew more than 100 people, was hosted by Smith's roommate with the linebacker's permission in June 2012 at Smith's spacious rental home in the unincorporated foothills east of San Jose. Dozens of people who saw fliers for the shindig showed up, many of whom paid a $10 cover charge to get through the door. Once inside, there was a DJ, dance area and fully stocked bar offering $5 drinks.

In addition to possible criminal charges, Smith also is facing a negligence lawsuit filed months ago by an Alameda County man, Ronndale Esporlas, who was shot in the leg during the party. The suit also names former 49er Delanie Walker, now with the Tennessee Titans. David Kleczek, the attorney representing Esporlas, did not return a phone call seeking comment.

Ballistics tests indicate that Esporlas and another man were not shot by Walker or Smith. Deputies have yet to identify the shooters in the ongoing investigation. But alleged gang member Steven Barda, 27, is in custody on charges of stabbing Smith, who sustained only minor wounds.

A second lawsuit has been filed against Smith and Walker, but the details of that complaint were not immediately available.

If prosecutors wind up charging Smith, they might have a tough time winning their case for several reasons.

Possession of assault weapons is a "specific intent" crime, meaning the prosecution must prove that Smith knew or should have reasonably known the guns were illegal. Investigators are currently looking into whether he purposely left California to buy the illegal guns. Smith could have easily modified the guns to comply with state laws by buying a "bullet button," which prevents the removal of the magazine without a tool.

The charge is known as a "wobbler," meaning it can be prosecuted either as a felony or misdemeanor. If it is filed or resolved as a misdemeanor, the maximum sentence would be a year in county jail, though probation is more likely.

In a statement, 49ers General Manager Trent Baalke said, "The 49ers organization has been aware of this matter concerning Aldon Smith for some time. We will continue to monitor the situation closely, but will have no further comment at this time, as this is an ongoing legal matter."